Did you know that there are totally a series of video game based off of The Prisoner? The more you know!
Nice list, I thought you had forgotten Zero from 9 hours, 9 Persons, 9 Doors but seeing as its just you haven't played it yet that makes sense, but you should totally play that game, it's fantastic!
I do recommend you avoid the 999 character pages for spoilers. The game page is currently safe though. Seemed to be the best way to go about things, though I tried to prod the other editors for help. Spoiler blocks in the new wiki design would be welcome.
The 999 characters relevant to this list are: Zero, Santa, Seven. Their names are actually numbers, and not metaphorically based on numbered things. (June doesn't mean 6, for example.)
If you add Ace and Snake, I'll be forced to stage a Snake Eyes filibuster. ()